PRISMA Experiment Operations at GSOC

The goal of PRISMA is to demonstrate sensors and flight software needed to perform formation flight and rendezvous missions. With respect to future on-orbit servicing missions, PRISMA is a milestone in developing and demonstrating the required technologies in orbit. The experiment operations started after commissioning and separation of the two spacecraft, Mango and Tango, in August 2010 . The basic experiment programme is planned to last ten months, with an additional two months for an extended campaign. The first half of this timeline was successfully executed by the Swedish Space Corporation, and after the transfer of operations on 14 March it is now GSOC's turn to conclude the nominal first year of operations. Let's have a closer look at the project structure, the experimenter's contributions and the experiment operations to be conducted at GSOC.

The project structure of the PRISMA mission initiated by the Swedish National Space Board (SNSB) is very international, including partners from all across Europe. As the project leader, the Swedish Space Corporation (SSC) is the spacecraft manufacturer and the provider of onboard software and experiment specific Guidance, Navigation and Control (GNC) flight software. Each of the project partners, being experimenters at the same time, has provided their own hardware and software for technology demonstrations during specific experiment slots.

Project Partners on the PRISMA mission

The key contributions in form of sensor and actuator components and experiment specific flight software are listed in the table below. The mission objectives are associated with different experiment slots. These connect hardware and specific flight software developed by the different experimenters to carry out the intended technology demonstration. Four operational and four equipment experiment sets are planned.

The four operational experiment sets are Autonomous Formation Flying based on GPS (AFF, SAFE) or FFRF (FFIORD) within a range of 10 kilometres to 20 metres, vision based Autonomous Rendezvous (ARV) at ranges of 100 kilometres down to 3 metres, Proximity Operations (PROX) based on GPS or VBS at 100 metres to 3 metres and vision based Final Approach and Recede Manoeuvres (FARM) at 3 metres to 0 metres. Additionally, DLR will perform a single spacecraft experiment within the Autonomous Orbit Keeping (AOK) slot.

Each project partner has setup their own Experiment Control Center (ECC), which will allow to remotely simulate experiments in advance, to monitor experiments from telemetry and to post-process the acquired data. All ECCs are coordinated by the Mission Control Center (MCC), which is located at DLR/GSOC for the next five months.

After providing the GPS-based navigation functionality consisting of the Phoenix-S receiver, antenna system and onboard real-time navigation software, the Precise Orbit Determination (POD), for experiment validation and successfully conducting the first experiment slots, GSOC is proceeding one step further by taking the responsibility of being the PRISMA mission control centre, including the associated experiment operations and their management. Due to the increased responsibility, additional experiment slots were granted to GSOC, so it will conduct an On-Orbit Servicing experiment (OOS) with a tumbling Tango satellite, based on GPS while simultaneously using the camera systems to acquire images of Tango for later ground-based processing. A Formation Flight Re-Acquisition experiment (FFReAc) will be conducted to bring the spacecraft close together after having drifted far away from one another during the AOK experiment.

The timeline to be executed is shown in the table below: experiment timeline during mission operations at GSOC. A mix of formation and single spacecraft operations will be conducted based on different sensor technology and flight software contributions from different project partners. A more in-depth description of the specific experiments, their objectives and results are to be expected in future blog contributions, so stay tuned.